import random
s=''
for i in range(0,4):
    if random.randint(0,1)==0:
        '''随机生成大写字母'''
        s=s+chr(random.randint(65,90))
    else:
        '''随机生成小写字母'''
        s=s+chr(random.randint(97,120))
print("字母验证码:",s)